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On Being and Essence

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A small error at the outset can lead to great errors in the final conclusions, as the Philosopher says in I De Caelo et Mundo cap. 5 (271b8-13), and thus, since being and essence are the things first conceived of by the intellect, as Avicenna says in Metaphysicae I, cap. 6, in order to avoid errors arising from ignorance about these two things, we should resolve the difficulties surrounding them by explaining what the terms being and essence each signify and by showing how each may be found in various things and how each is related to the logical intentions of genus, species, and difference.


Since we ought to acquire knowledge of simple things from composite ones and come to know the prior from the posterior, in instructing beginners we should begin with what is easier, and so we shall begin with the signification of being and proceed from there to the signification of essence.

79 pages, Paperback

First published January 1, 1256

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About the author

Thomas Aquinas

2,522 books1,086 followers
Philosophy of Saint Thomas Aquinas, a Dominican friar and theologian of Italy and the most influential thinker of the medieval period, combined doctrine of Aristotle and elements of Neoplatonism, a system that Plotinus and his successors developed and based on that of Plato, within a context of Christian thought; his works include the Summa contra gentiles (1259-1264) and the Summa theologiae or theologica (1266-1273).

Saint Albertus Magnus taught Saint Thomas Aquinas.

People ably note this priest, sometimes styled of Aquin or Aquino, as a scholastic. The Roman Catholic tradition honors him as a "doctor of the Church."

Aquinas lived at a critical juncture of western culture when the arrival of the Aristotelian corpus in Latin translation reopened the question of the relation between faith and reason, calling into question the modus vivendi that obtained for centuries. This crisis flared just as people founded universities. Thomas after early studies at Montecassino moved to the University of Naples, where he met members of the new Dominican order. At Naples too, Thomas first extended contact with the new learning. He joined the Dominican order and then went north to study with Albertus Magnus, author of a paraphrase of the Aristotelian corpus. Thomas completed his studies at the University of Paris, formed out the monastic schools on the left bank and the cathedral school at Notre Dame. In two stints as a regent master, Thomas defended the mendicant orders and of greater historical importance countered both the interpretations of Averroës of Aristotle and the Franciscan tendency to reject Greek philosophy. The result, a new modus vivendi between faith and philosophy, survived until the rise of the new physics. The Catholic Church over the centuries regularly and consistently reaffirmed the central importance of work of Thomas for understanding its teachings concerning the Christian revelation, and his close textual commentaries on Aristotle represent a cultural resource, now receiving increased recognition.

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5 stars
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147 (21%)
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Displaying 1 - 30 of 75 reviews
Profile Image for David Haines.
Author 10 books134 followers
September 19, 2022
I have read through this book numerous times, and each time I am impressed by Aquinas's clear treatment of this subject. It is a difficult subject, and reading this book requires much concentration, but the person who perseveres is greatly rewarded for the hard work required to understand this subject.
Profile Image for Jacob Aitken.
1,679 reviews405 followers
February 15, 2022
Thomas Aquinas, On Being and Essence. Trans. Armand Maurier. Toronto: Pontifical Institute of Mediaeval Studies, 1968.

It’s hard to know where to start with Thomas Aquinas. His various Summas are important, but that is a steep learning curve and also demands a good, working knowledge of secondary Thomist literature. I think this current volume might be the best place to start. It is short and focused, whereas the Summa is close to being a transcript of an oral Master's thesis. The introduction by Armand Maurier makes this volume doubly good.

The argument at its most basic: being as esse is the actuality of being, the act of existence. Think of it along more dynamic lines. Being as ens is the substance that has the actuality of being. Whatever esse an ens has, the esse structures the ens.

Citations from this book will be by chapter and section. “1.1” is chapter one, section one.

“Essence must be something common to all the natures through which different beings are placed in different generas and species” (Aquinas 1.3). Neither form nor matter is an essence. Matter cannot be an essence because it is not a principle of knowledge (2.1). It can’t be either because both are needed for the being of a substance.

Key ideas: “The genus, then, signifies indeterminately everything in the species and not the matter alone” (2.8). It is the “whole” of a thing without its “this-ness,” or specific form. A genus is proportionate to the whatness of a thing; specifies to its form; and difference to the composite nature (2.9).

Human nature isn’t the form itself or the matter itself, and if we can’t know it through the matter, how do we know it? Human nature has its being in the intellect abstracted “all individuating factors” (3.6).

On Predication

We predicate something when our intellect combines and divides things (3.8).

A form is only intelligible when it is abstracted from matter, and only something immaterial can abstract it.

Key idea: a being is either uncaused, caused by the principles of its being, or receives its being from outside itself. Therefore, everything whose being is distinct from its nature receives its being from another (4.7). Thomas suggests, though doesn’t really develop it, that one could extend this chain to the first cause, pure being.

You don’t have to agree with Thomas Aquinas. I am more of a Scotist myself when it comes to knowledge of God and the human will. But if you are unfamiliar with the arguments in this book, and you choose to criticize Thomas Aquinas, then you deserve something like what happened when Ed Feser reviewed Jeffrey Johnson’s book on Aquinas.
Profile Image for Viji (Bookish endeavors).
470 reviews158 followers
May 31, 2014
A brilliant text on the topics of being and essence. Throughout the text,one can see the influence of Aristotle(the major influence,of course),Avicenna and Boethius.
In the first part,the concepts of being and essence are defined. Then it move on to essences of simple and composite substances. The concepts of genus and species are dealt with in the next step. How essence is found in substances is discussed in the next part. The entire theory part is borrowed from Aristotle. We can see the concepts of potentiality and actuality and form and matter appearing throughout. As an independent text based on Aristotelian theories,this text does justice to the master. The only problem I felt was the constant interference of God. Whenever a definition is put forth,there is given an exception with it,reserved for God. But that can't be helped since the author is Aquinas.
The text is written in clear language and is easily comprehensible,for those with a basic knowledge of classical western philosophy.
Profile Image for María Carpio.
382 reviews302 followers
December 9, 2023
A parte del Suma Teológica, creo que esta es una de las obras cruciales de Tomás de Aquino, pues aquí explica desde la lógica y categorías aristotélicas las nociones de ente y esencia, a través del los conceptos de ser, materia, forma, naturaleza, esencia o quididad, género, especie, accidente y diferencia adaptadas a la teología. Y, con ello explica también la existencia de Dios, a quien define como la causa primera. Para ello, desarrolla la idea de que el ser, al estar compuesto de forma sustancial y materia, tiene una esencia/quididad a causa de ello. Ésta esencia en las inteligencias debe tener una existencia aparte de la forma (la forma sustancial es la esencia) y por eso Aquino sostiene que la inteligencia es forma y existencia. Pero, todo aquello que conviene a algo o es causado por su propia naturaleza (la risa en el hombre, por ejemplo), le viene de un principio exterior, así como la luz en la atmósfera es por causa del sol. Asimismo, Aquino sostiene que la existencia no puede ser causada por la propia propia forma o la quididad (esencia) de la cosa (o del ser), pues todas las cosas cuya existencia es distinta de su naturaleza, existen por causa de otra. Y por ello es que es necesario que exista una causa primera y que ésta sea causa del resto de existencias por ser ella misma únicamente existencia, pues sin ella nos iríamos al infinito de las causas precedentes. Y esa primera existencia, ese primer ente que es existencia solamente, es Dios, según Aquino.

Esta pequeño tratado, bastante complejo de leer, tiene varias disquisiciones más acerca de los conceptos y categorías sobre el ser desarrolladas por Aristóteles, en las cuales hace uso de los comentaristas aristotélicos Averroes y Avicena, y por ello hay que por lo menos tener claras las categorías y nociones que desarrolla Aristóteles en su obra Metafísica, pues si no, se corre el riesgo de no entender nada. Una vez claras esas nociones, la lectura se puede facilitar. En esta reseña he condensado prácticamente una parte o capítulo del libro, que creo que es el summum de su teoría, la cual ha trascendido durante siglos y ha sido base de la teología racionalista y en gran medida uno de los pilares fundamentales de la filosofía post-clásica. Es importante decir que Tomás de Aquino con su teología (filosófica) desarrollada a partir de Aristóteles (por lo que no recibió pocas críticas en su tiempo) fue el primer pensador cristiano católico (Doctor de la Iglesia) en unir la fe y la razón desde la filosofía y la teología, con lo que aportó enormemente al desarrollo del pensamiento occidental. Tomemos en cuenta que fue escrito en 1256 durante su estancia en París como profesor de los frailes dominicos en el convento de Saint-Jacques, por lo que este texto es una preparación para sus clases.
Profile Image for rhapsodyof words.
8 reviews
May 19, 2014
I didn't understand a single word...It was like i was reading a book in Chinese.
Profile Image for Michael Pecha.
25 reviews4 followers
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June 23, 2022
Who said ontology was boring 😐. Doesn’t feel right to place stars on this book because it’s Aquinas but it was very dense, confusing, and boring (as Aquinas usually is - don’t hate me for saying that).

However, despite being dense, confusing, boring… once the concepts and stuff are explained (by a competent teacher) the beauty of existence and being is truly laid out before the reader as a veritable feast. This text may seem to be of little value in the beginning, but after more reflection/discussion (with lots of handholding from the prof) on the topic of being, there is a large payoff.

Aquinas has once again shown his genius in this text, a pity I’m not smart enough to appreciate/understand it in its entirety. Oh well.
Profile Image for Dougald.
118 reviews15 followers
April 1, 2017
I have to admit, a large part of this was over my head. I have never been great at understanding works on ontology. First, every single time he talked about "quiddity" I thought of Quidditch.

With that said, perhaps a return to this discussion would be helpful for our current cultural climate. It seems that the accidents are being exalted over the essence when it comes to sexuality. The individuality is being exalted over the essence. In fact, towards the end, Aquinas connects these ideas with race (though he doesn't use those words).

In short, I probably needed to read this slowly and with someone else who knows philosophy better. But, it was a short challenging read.
Profile Image for sch.
1,266 reviews23 followers
December 16, 2015
Very short, still too hard for me. Will try again but I need something more elementary.

Update: Raising my rating after reading the translator's brief and lucid introduction.
Profile Image for Audrey.
30 reviews5 followers
October 6, 2024
Une lecture brève mais éclairante quant aux notions essentielles de la métaphysique thomiste. Pour ce qu'il en est de Dietrich de Freiberg, la réfutation des thèses de Thomas d'Aquin m'a paru assez superficielle et sophistique et dotée d'une portée philosophique nettement moindre...
Profile Image for DeaFlourishment.
114 reviews126 followers
March 3, 2024
Estoy haciendo relectura del texto para un seminario de Agustín de Hipona y Tomás de Aquino. No recordaba lo árido y lo complejo que resulta seguir estas temáticas.
Profile Image for Italo Lins Lemos.
53 reviews4 followers
May 9, 2022
Leitura obrigatória para todos(as) que têm interesse em metafísica, mesmo que seja para discordar do autor. O texto é curto, mas é certamente um daqueles que te fazem passar algumas horas para avançar algumas poucas páginas - não por falta de clareza, mas pela complexidade da temática.
Profile Image for Peter.
53 reviews
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March 12, 2023
Dici potest quia quidquid legitur legitur secundum modum legentis. Ergo hic lector carens arte latinitatis non totum intellegere potuit. Quod non mirandum est—etiam editionem anglicam cum difficultate lego. Sed qui discit non solum ad modum suum apprehendit, sed sicut docentis. Et Doctor Angelicus magister bonus.
11 reviews2 followers
August 23, 2022
I’m too dumb to appreciate it enough to give it 5 stars. I had to read other commentaries to affirm I was reading it correctly, and I still think there’s more to his arguments that was absorbed.
Profile Image for Greg Samsa.
78 reviews3 followers
October 17, 2023
Absoluter Banger. Manche Stellen rafft man beim ersten Lesen nicht, aber hat mir super geholfen nen Einstieg in Aquin und auch Aristoteles zu finden.
Profile Image for Uğur.
472 reviews
January 23, 2023
Before starting with the views of Thomas Aquinas that make up the philosophy of Christianity, I think it is necessary to start by briefly touching on Aristotle's philosophy of being, which he was very inspired by. Aristotle, on the subject of being, reveals that those who exist do not exist alone, that every being has a 'meaning of being', and reveals that the separation of the phenomenon of being that can be separated in thought is impossible in reality. At this point, there is a reference to the phenomenon of god-nature, which is one of the first topics of philosophy in the narrative of the totality of being through the soul-body relationship. As a result, the existence of God and nature is integrated on the basis of uniqueness.

Based on this point, Aquinas emphasizes integrity about being and essence. But he does it in the context of man and nature. At this point, he has separated from the Aristotelian philosophy and considers it in a different way by Deciphering the meaning of the existence of God among the meanings of being within the framework of Christianity. Although it Deconstructs the integrity of Aristotelian metaphysics in a philosophical sense, it has introduced an abstraction between beings (God-man-nature) in the philosophy of monotheistic religion. This content, which you will find in the book content, also symbolizes the philosophical infrastructure of medieval Europe. I didn't really like this book, which also contains a general explanation of the philosophy of monotheistic religions, because I opposed it in many parts, but it can serve as a good resource for readers interested in theology. Pleasant reading already. Live by transcending those who limit and isolate you. Amen.
Profile Image for Andrew Noselli.
675 reviews66 followers
June 7, 2024
In today's Postmodern existential world, the Be-ing of existence precedes essence, just as substance precedes the prescribed form it will take, for the mode and the pattern have been formalized and codified for hundreds and years by this time, to such a point that politics takes precedence over all thoughts of God.
82 reviews
September 17, 2024
Excellent work by Thomas Aquinas, as always! It's a bit shorter than I was expecting, and I don't agree with some of the axioms Aquinas draws from, but his logic is sound. As always, Aquinas is a joy to read!
Profile Image for Rory Fox.
Author 9 books41 followers
January 3, 2024
At around 10,000 words (in English) this is a relatively short introduction by Thomas Aquinas (d.1274) to medieval philosophical concepts essence and existence.

Chapter 1 distinguishes between two easily confused ideas of existence. Things can exist in reality (eg a tree ‘is’). But concepts are also predicated linguistically (eg a unicorn can be said to be 4 legged). The difference between real things and linguistic entities is a critically important starting point for philosophy.

Chapter 2 focuses on the first type of existence, exploring how ‘things’ have essences. We hear that entities like trees have an essence, which we can think of as its nature. While our experience of reality is an experience of material things, nevertheless immaterial things (like a square) can also have an essence.

Chapter 3 focuses on the second type of existence (ie linguistic). It explains how we have essences within the linguistic definitions and intentional ideas within our minds (eg unicorns).

Chapter 4 carries the discussion on to explore how the concept of ‘essence’ applies to a unique set of entities which are unlike the physical or mathematical entities in chapter 2. These are ‘separated substances’ like angels and souls, which share the reality of physical things, but the immateriality of mathematical entities.

Chapter 5 is a recapitulation of earlier discussions, comparing and contrasting how concepts of existence and essence are applied to the different kinds of entities discussed in chapters 2-4.

Chapter 6 closes the treatise by applying the ideas of essence and existence to ‘accidents’. These are (like) the properties predicated of things. A tree has an essence and an existence (chp 2) but it might also be described as ‘tall.’ The tallness of the tree has a kind of existence of its own, as tallness can be defined. But tallness cannot exist on its own, so it is an 'accident,' which can only be said to have an essence or existence in an extended sense of the words.

Overall, this is a difficult read for modern thinkers who are unfamiliar with medieval language. But it is also a relatively clear and straightforward introduction to that medieval thought world, for students who wish to understand it better . However, an important limitation of the book is that it cannot include consideration of issues raised after Aquinas' death, by critics such as Scotus.
Profile Image for Argiris Fakkas.
302 reviews18 followers
February 3, 2023
Ένα πολύ δύσκολο φιλοσοφικό βιβλίο του Θωμά Ακινάτη πάνω στην οντολογία. Μέχρι τα μισά του δεύτερου κεφαλαίο κάτι γινότανε όσον αφορά την κατανόηση του κειμένου, μετά τα πράγματα εκτραχύνθηκαν και το κείμενο έγινε πολύ δύσκολο, ιδιαίτερα στο έκτο κεφάλαιο με τα συμβεβηκότα. Όταν διαβάζεις ένα βιβλίο στο οποίο το ίδιο το φιλοσοφικό κείμενο είναι μικρότερο σε μέγεθος από τις υποσημειώσεις του αυτό και μόνο τα λέει όλα. Μόνη εξαίρεση είναι η αρκετά καλή και κατατοπιστική εισαγωγή, που όμως από μόνη της δεν σώζει την κατάσταση.

Profile Image for David Haines.
Author 10 books134 followers
March 27, 2013
This book is a wonderful translation and commentary on a very difficult and profound pamphlet that was written by the young Aquinas. The difficult and profound pamphlet is the well-known "Esse et Essentia", and in this pamphlet Aquinas sets out to pose solid foundations for philosophy and theology. In order to avoid error one needs to ensure that their starting point is sure. As such, Aquinas sets out to explain what is meant by the words "Being" and "essence", how they are found in diverse things, and how they are related to the logical intentions. Joseph Bobik gives an indepth analysis and commentary on Aquinas's treatise, which is, essentially, one of the best textbooks that a professor could use for an advanced course in Thomistic Metaphysics.
Profile Image for Michael.
67 reviews
January 24, 2009
Being were I am, I am supposed to be more in love than Thomas than what I am.

On the matter, I'm either too ignorant to be enlightened or too enlightened to be ignorant, but either way I'm too ignorant to know which.

1/2 star for Thomas's ending... "having said this we may make a proper end to this discourse. Amen."

having said this, I make an end to this review. Amen.
Profile Image for Rob.
278 reviews8 followers
December 31, 2008
Bobik's translation is very readable, though it does not include the original Latin for quick comparison. His commentary is illuminating as it includes exposition of the text as well as detailed articles on Aquinas metaphysical views.
352 reviews57 followers
July 21, 2014
Basically three-quarters Aristotle and what Averroes thought of him, which was expected, but gets kind of fun with Aquinas playing around with his genus-less, species-less God (whose existence is His own quiddity, let's remember, but that doesn't deny Him an essence!).
Profile Image for Genndy.
329 reviews10 followers
March 10, 2016
This is a very short and inadequate introduction to the thought of Thomas Aquinas. Besides this introduction lacking depth, it is also a fact that Aquinas' thought isn't that impressive at all, with it's subjective metaphysical deduction.
Profile Image for Emerson John Tiu Ng.
436 reviews9 followers
May 5, 2015
..this book is so hard to read especially if you are not a Philosophy graduate.....
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